1. Field of the Invention
The present invention relates generally to methods of producing spinel Li.sub.2 Mn.sub.2 O.sub.4, and particularly, but not by way of limitation, to methods of producing spinel Li.sub.2 Mn.sub.2 O.sub.4 for use as a cathode material in rechargeable lithium batteries.
2. Description of Related Art
Various types of rechargeable batteries are known in the art. One such family of rechargeable batteries is the familiar nickel-cadmium (ni-cad) battery and another such family of rechargeable batteries is the nickel-metal-hydride battery. Yet another family of rechargeable batteries utilize an anode fabricated of carbon in conjunction with a cathode fabricated of a lithium based composition, such as LiCoO.sub.2, LiNiO.sub.2 or spinel Li.sub.2 Mn.sub.2 O.sub.4. Because the batteries utilizing the lithium based compositions have a high discharge voltage of about 4 volts and thus an energy density about twice that of the nickel-cadmium or the nickel-metal-hydride batteries, the batteries utilizing the lithium based composition represent the state of the art in small-size rechargeable batteries. New and improved rechargeable batteries are constantly being sought, thus, the prior art is replete with lithium based compositions wherein the compositions are produced in various ways.
As an example, U.S. Pat. No. 5,196,279 issued to Tarascon discloses a method of producing spinel Li.sub.2 Mn.sub.2 O.sub.4 wherein LiMn.sub.2 O.sub.4 is reacted with LiI at low temperatures, or by refluxing LiMn.sub.2 O.sub.4 in an acetonitrile solution of LiI.
As another example, Lithium Intercalation from Aqueous Solutions, J. Electrochem. Soc., Vol. 141, No. 9, September 1994, page 2310, authored by W. Li, W. R. McKinnon and J. R. Dahn discloses a method of producing spinel Li.sub.2 Mn.sub.2 O.sub.4 in an aqueous LiOH electrolyte, or by reacting LiOH with LiMn.sub.2 O.sub.4 in a solid-state reaction.
Although spinel Li.sub.2 Mn.sub.2 O.sub.4 cathodes formulated in accordance with the work described by W. Li, W. R. McKinnon, J. R. Dahn, Tarascon and others have generally exhibited the desired physical qualities of a high discharge voltage and thus a high energy density, new and improved methods of producing spinel Li.sub.2 Mn.sub.2 O.sub.4 are desired which do not require the use of solvents or the use of relatively expensive compounds. It is to such an improved method for producing spinel Li.sub.2 Mn.sub.2 O.sub.4 that the present invention is directed.